1. Field Of The Invention
This invention relates to face-to-face plate-type swivels which are widely used for supporting an article rotationally upon a base, viz: a chair seat upon a chair base, a television set upon its base, etc.
2. Description Of The Prior Art
It has been customary for many years past to employ centrally securable upper and lower swivel plates spaced by an interposed circular series of spaced ball bearings arranged in complementary circular grooves or races.
The LeBlanc U.S. Pat. No. 3,120,982 notes the objections, deficiencies and limitations of ball bearing swivels and proposes to provide a noiseless, greaseless, durable and inexpensive swivel joint by mounting a Nylon ring permanently in each race to provide Nylon-to-Nylon bearing contact between plates.
Other patents, which replace ball bearings with frictionless plastic material are the Niemi and Faull U.S. Pat. Nos. 3,445,147 and 3,574,427. They identically disclose a pair of circular "frictionless" plastic rings arranged one upon the other between centrally securable upper and lower swivel plates to facilitate the rotation of one plate relative to the other and stop means preventing relative movement between each ring and its adjacent plate upon relative rotary movement between the plates.
In all three of the foregoing patents, one rotary plate and the adjacent plastic ring rotate as a unit relative to the other plate and its adjacent ring. Also all plates are centered by centering means extending along the axis of rotation.